The field of invention is gear housings, more particularly gear housings for a motor vehicle window lift drive.
In a known motor vehicle window lift drive, a rotatably driven worm drive shaft engages a toothed gear, such as a worm wheel, disposed in a gear housing. The worm wheel has an output shaft with one end extending radially through the gear housing for rotatably driving a window lift mechanism. An opposite end of the output shaft extends radially into a backwall of the gear housing. The backwall supports the output shaft by counteracting forces exerted onto the backwall by the output shaft.
In addition to axial forces, the output shaft transmits radial and tangential forces developed at the worm wheel toothing and worm drive shaft interface. These forces are absorbed by the backwall by various means and methods. One known housing provides sufficient structural integrity in the housing backwall by providing a thickened backwall wall. However, a thickened plastic or metal housing adds unnecessary weight to the overall mechanism and requires a greater amount of material to fabricate than other alternatives.
Another known housing incorporates strengthening ribs in the backwall to provide support and structural integrity in key locations. This housing requires less material and, therefore, provides a lighter housing that is less expensive to produce than the method described above. The ribs, however, require fabrication of the housing with varying wall thicknesses that concentrate stresses increasing the potential for fatigue failure and require looser fabrication tolerances increasing material requirements.